1. Field of the Invention
The present invention relates to an airbag apparatus mountable on a vehicle and including an airbag inflatable with inflation gas and protruding from a housing where the airbag was folded and housed. More particularly, the present invention relates to an airbag apparatus whose airbag includes an outer bag and an inner bag disposed inside the outer bag, and which is suitably used for a steering wheel or a front passenger's seat.
2. Description of Related Art
A conventional airbag apparatus mountable on a vehicle includes an airbag inflatable with inflation gas and protruding from a housing where the airbag was folded and housed. As shown in JP 9-220995 A and in JP 2001-080440 A, such an airbag is attached to the housing at a periphery of its opening for admitting inflation gas. The airbag includes an outer bag constituting an outer wall of the airbag and an inner bag disposed inside the outer bag over the inlet opening. The inner bag is provided with an outlet port for allowing the inflation gas fed from the inlet opening to flow out into the outer bag.
The outlet port of the inner bag is used to redirect the inflation gas flowing out into the outer bag in order to control an inflated contour of the outer bag from the initial stage until the completion of inflation. For example, the outlet port is used to control the contour of the outer bag such that the deployment of the outer bag to an abdomen of a driver is promoted. That is, the inner bag of the airbag helps redirect the inflation gas flowing out into the outer bag.
However, there has been a room for improvement in conventional airbag apparatuses in inflating the outer bag without allowing a region of the outer bag deployed proximate the housing to float from members disposed around the housing during the course of inflation.
The floating of the outer bag from the members disposed around the housing is likely to cause a swaying motion of the outer bag where the outer bag floats from the members disposed around the housing and falls back to bump against the members repeatedly during the course of inflation. In the floated state, the outer bag being inflated is not supported by the members disposed around the housing, which makes it difficult for the outer bag to secure an enough reaction force for exerting cushioning property for receiving an occupant. On the other hand, if the outer bag engages the occupant in a thickening phase during the swaying motion, the bag may press the occupant unduly.